LED lighting system

ABSTRACT

A system and method involving lighting fixtures, a control network, a controller and other devices such as light sensors, input devices and network adapters for coordinating precise brightness and color schedules among the lighting fixtures while maintaining a high color reliability including provisions for managing a plurality of lighting fixtures. The lighting fixtures contain lighting elements selected such that when controlled properly, operating along a daytime locus, the resultant light output closely resembles sunlight on a cloudless day in spectral characteristics, and wherein the total flux of blue light can be adjusted from a relative level of 1-100% the maximum blue flux of the lighting fixture by controlling individual lighting elements.

BACKGROUND

Technical Field

The present invention generally relates to the field of lightingdevices, and more particularly, to a system and method of controllinglighting fixtures for coordinating precise brightness and colorschedules so as to closely resemble sunlight on a cloudless day inspectral characteristics.

Description of the Related Art

With growing demand for energy efficient lighting, new lightingtechnologies such as LEDs offer distinct opportunities due to theircustomizable colors and precision in control. As the white LED lightingmarket grows, advancing the state of the art entails a seamlessintegration of artificial light with natural light and healthfullighting through dynamic lighting.

One particular niche of such LED design and control is in the generationof artificial sunlight for variety of reasons, especially for treatinghuman ailments, e.g., circadian rhythm disorders, seasonal affectiondisorders, shift work conditions, etc.

U.S. Pat. No. 6,350,275 (Vreman et al.) relates to a pair of personalglasses with built in LED's within 3 cm of the eye which directs red andblue light into the user's eyes to treat circadian rhythm disorders.However, this invention is limited to one user, must be worn during theworking period and does not simulate natural sunlight.

The following patents propose similar methods of treating circadianrhythm disorders, but wherein they do not replicate natural sunlightconditions, involve a portable or wearable device, involve treatmentperiods which are intermittent and require that the patient engage withthe device, or involve chromatic properties of treatment light which arenot defined: U.S. Pat. No. 5,503,637 (Kyricos, et al.); U.S. Pat. No.6,053,936 (Koyama, et al.); U.S. Pat. No. 5,197,941 (Whitaker); U.S.Pat. No. 5,545,192 (Czeisler, et al.); U.S. Pat. No. 5,176,133(Czeisler, et al.); and U.S. Pat. No. 5,304,212 (Czeisler, et al.).

Examples of other lighting control systems are mentioned below:

U.S. Pat. No. 7,014,336 (Ducharme, et al.) relates to active circuitrywith a feedback mechanism for reading the light in the room and activelyadjusts. In particular, the invention relates specifically to colortemperature variable lighting fixtures but without relating a specificregion of the blackbody curve or chromaticity diagram. It also does notappear to teach or suggest a method for automatically adjusting thecolor temperature and brightness of the lighting fixtures without userinput.

U.S. Pat. No. 7,213,940 (Van De Ven et al.) involves reducing light withspecific coordinates (dimming and feedback) utilizing different familiesof LED emitters and adjusts for specific output at constant colortemperature at a sacrifice of brightness. This patent is also staticembedded systems with controls within the fixture. This inventionrelates to a variable color temperature adjustable over time with activecontrols. In particular, the invention involves a specific 5-sidedbounding box on the CIE (Commission Internationale de l'Eclairage) 1931chromaticity diagram. It specifies that a first group of lightingelements must have chromaticity coordinates at a first point (defined)and a second group must have coordinates falling within the defined box.Additionally, this patent relates to a lighting fixture producing afixed color temperature.

U.S. Pat. No. 7,354,172 (Chemel, et al.) relates to rendering lightingconditions based on a reference color gamut common to many lightingunits in a network using white and monochromatic LEDs. This patent doesnot specifically define the color gamut or the colors or chromaticitycoordinates the fixture operates at, and does not appear to teach orsuggest a means by which brightness and color are autonomously anddynamically changed with time.

U.S. Pat. No. 6,459,919 (Lys, et al.) discloses illumination of livingtissues where known light parameters relate to a condition of the livingtissue. This is discussed in the context of using light to identifyabnormal features and pathological conditions of tissues, living matter,and other materials. The therapeutic applications mentioned in thebackground extend only to diagnostic methods, and do not appear to teachor suggest using lighting conditions to stimulate a biological response.

U.S. Pat. No. 6,441,558 (Muthu, et al.) relates to a fixture employingred, green, and blue LEDs and a control mechanism such that the fixtureoutputs a constant color temperature and brightness.

U.S. Pat. No. 6,340,868 (Lys, et al.) relates to lighting units on anetwork capable of receiving addressing commands and controls forcontrolling a plurality of LEDs in each unit. However, this inventiondoes not deal with methods by which lighting conditions are changed(i.e., color schedules), specific chromatic regions the fixturesrecreate, or methods to ensure color consistency (i.e., feedback loopsor sensors).

U.S. Pat. No. 7,173,384 (Plotz, et al.) relates to recreating apredetermined region on a CIE chromaticity diagram using pulse widthchannels of red, green, and blue LEDs arranged in channels of up to six.

U.S. Pat. No. 7,067,995 (Gunter, et al.) discloses the use of atemperature sensor and calibrations, along with sensor calibration datastorage at various reference temperatures as a means of correcting colorfluctuations related to the thermal state of the LEDs.

U.S. Pat. No. 6,992,803 (Chang) relates to a feedback mechanism whichcalculates the chromaticity coordinates of each lighting element in alighting fixture to calculate the proper operating conditions necessaryto reproduce a specific chromaticity coordinate.

U.S. Pat. No. 6,683,419 (Kriparos) discloses a method by which LEDs,with linear dimming-brightness curves, mimic incandescent bulbs, whichhave exponential dimming-brightness curves. The invention involves thedimming-brightness relationship in an LED fixture and does not appear toteach or suggest changing color with dimming level.

U.S. Pat. No. 7,327,337 (Callahan) involves a series of lighting devicesconnected to a two wire power bus in which the color modulation signalsare transmitted through the power connection and demodulated in thelighting device.

U.S. Pat. No. 6,806,659 (Mueller, et al.) covers a lighting controlnetwork for LED luminaires as well as various LED lighting fixtures forseveral applications. See also U.S. Patent Publication No. 20040178751(Mueller, et al.).

U.S. Pat. No. 4,962,687 (Belliveau, et al.) deals with variable colorsin a lighting system achieved by dimming circuitry within fixtures. Itdoes not appear to cover specific chromatic regions rendered using acontrol feedback loop.

U.S. Pat. No. 5,350,977 (Hamamoto, et al.) involves a variable colortemperature fixture, and does not incorporate a means of autonomouslyand dynamically changing the color temperature and or brightness withrespect to the time of day or geographic location.

U.S. Pat. No. 5,357,170 (Luchaco, et al.) claims a control system wherepreset conditions can be changed by the occupant by moving a physicalmember or slider control to change the maximum brightness levels of thesystem. This patent does not appear to address color modulation overtime or lighting schedules or programs.

U.S. Pat. No. 7,288,902 (Melanson) deals first with a lighting fixturewith two unique lighting elements, each possessing a fixed colortemperature, which are then dimmed at different ratios relative to theAC power dimming level to achieve a variable color temperature withdimming level. This patent claims only “white” and “yellow” LEDs, anddoes not appear to teach or suggest the ratios or specific chromaticregion rendered by the lighting device. This patent also does not appearto teach or suggest any method by which a control system can interfacewith a fixture, or any method by which the brightness and colortemperature of the fixture can be controlled independently.

U.S. Pat. No. 6,720,745 (Lys, et al.) discloses the use of the RS-485standard to control a plurality of LED devices.

U.S. Pat. No. 7,215,086 (Maxik), issued relates to integrating thefixture designs within the Lutron Circuits to achieve diming levelsbelow 5% through pulse modulation. This invention utilizes a square wavewhich has been discussed in prior art.

U.S. Pat. No. 5,193,900 (Yano, et al.) discloses a device which detectsnatural light and mechanically actuates a filter on an artificial lightsource.

U.S. Pat. No. 6,554,439 (Telcher, et al.) teaches a method of treatingcircadian rhythm disorders using light sources and a rotating filter.

U.S. Pat. No. 7,446,303 (Maniam, et al.) discloses an ambient lightsensor suitable for determining lighting conditions, but does notpractice a lighting device or a system of lighting devices.

U.S. Pat. Nos. 7,387,405 and 7,520,634 (Ducharme, et al.) pertain to asystem of lighting devices capable of producing a broad range oflighting conditions, however they do not utilize a specific collectionof at least three lighting elements of a characteristic chromaticity (asis disclosed in the present application, as will be discussed later),and do not teach a method by which the user can prescribe a particularflux of blue light within white light.

U.S. Pat. No. 7,319,298 (Jungwirth, et al.) relates to a luminairesystem which produces light of a desired chromaticity and luminous fluxoutput with varying ambient temperature. The prior art teaches a methodby which the luminaire regulates chromaticity throughout changingtemperatures using sensors.

U.S. Pat. No. 5,721,471 (Begemann, et al.) discloses a lighting systemwhich manipulates artificial lighting based on actual lightingconditions, determined either by a light sensor exposed to natural lightor by the calendar day and time of day. It also discusses modificationto artificial lighting conditions based on a modification to presentmean day-lighting levels. In contrast (as will be discussed in detaillater), the present invention relates a desired result or circadianresponse to the generation of signals to control lighting devices andthe ultimate generation of artificial light. This method of input isbased on user preference rather than a prescriptive input based on adefault time of day or existing lighting conditions for a fixedgeographic location. The present invention allows the user to adjust forjet lag after travel, maintain the lighting conditions of a fixedgeographic location throughout any location, coordinate the circadianrhythm to a cycle other than 24 hours, or specify a desired circadianresponse or condition.

U.S. Pat. No. 7,679,281 (Do Hyung, et al.) teaches a lighting devicewith three lighting elements, two of which comprise an LED chip combinedwith a phosphor of a specific composition and a third LED chip whichemits light in the visible range of 580 nm or more. This third lightingdevice emitting visible light of 580 nm is described as a lightingelement which produces light of 3000K or less, however no specificspectral distributions of light are disclosed. In contrast (and as willbe discussed in detail later), the present invention relates to acollection of lighting elements with specific chromaticitycharacteristics such that the flux of blue light can be preciselycontrolled through independent modulation of each lighting element whilemaintaining high color rendering index of the artificial white light.The selection of the lighting elements in the present invention maycomprise any collection of lighting elements which produce light in thecharacteristic chromaticity regions described in FIGS. 13A-14B of thepresent application. Furthermore, it is within the scope of the presentinvention that any lighting device of a characteristic chromaticityillustrated in FIGS. 13A-14B of the present application be used togenerate artificial light of high color rendering index in the range of1800-6500K. These lighting devices may be composed of (but are notlimited to) LED chips, LEDs combined with phosphors, LED chips combinedwith quantum dots, LED chips combined with photonic crystals, organiclight emitting diodes (OLED), or polymeric LED devices (PLED).

U.S. Patent Publication No. 20030133292 (Mueller, et al.) discloses manyapplications of color temperature variable lighting. Daylight simulationand circadian rhythm disorder treatment is not mentioned.

U.S. Patent Publication No. 20030100837 (Lys, et al.) relates totherapeutic effects achieved with LED devices; it claims: an LED systemfor generating a range of colors within a color spectrum, selecting fromthe range of colors a set of colors, whereby the set of colors producesin the patient a therapeutic effect, and illuminating an area of thepatient with the set of colors for a period of time predetermined to beeffective in producing the therapeutic effect. The patent does notappear to identify the range of colors which produce the therapeuticeffect, nor does it appear to identify a period of time or method ofmodulation of the light to facilitate this therapeutic effect.

See also the following U.S. patent publications regarding LED lightingcontrols: U.S. Patent Publication Nos. 20050253533 (Lys, et al.);20050236998 (Mueller, et al.); 20050231133 (Lys); 20050218870 (Lys);20050213353 (Lys); 20050200578 (Lee, et al.); 20050151489 (Lys);20040212321 (Lys, et al.); and 20040105264 (Spero).

However, despite the foregoing, there remains a need for a system andmethod that generates broad spectrum white light of color temperatures1800K to 6500K in interior spaces using general lighting fixtures (e.g.,for treating circadian rhythm disorders) and wherein brightness andcolor are autonomously and dynamically changed with time and while usingcombinations of white LEDs and color LEDs. Furthermore, there remains aneed for such a system and method that does not require calculatingchromaticity coordinates but rather uses calibration values of sensoroutputs at specific color temperatures and preferably, for controlling afeedback loop, and a color matching algorithm.

BRIEF SUMMARY

The invention also comprises a novel method to control lighting devices(e.g., novel methods of interpreting given user input into controlsignals which translate to a specific point on the daylight locus orcolor temperature) as well as a novel lighting device. This issignificant because variable color temperature fixtures (e.g., thoseshown in the prior art) are designed to be controlled, operated, orprogrammed by lighting designers or advanced users. As will be discussedin detail below, the present invention incorporates methods by whichsimple inputs are translated into appropriate signals for controlling amulti-channel lighting device. These simple inputs may comprise

1) dimming level;

2) dimming level and color temperature level;

3) time of day;

4) time zone;

5) geographic location;

6) desired circadian response;

7) present activity (e.g., sleep, reading, working, studying, eating,resting, etc.); and

8) angle of sun.

These inputs can be manually inputted to the system or they can beautomatically fed to the system from sensors (e.g., clocks, globalpositioning systems, etc.).

A further input to this novel system is the flux of color light, andmore preferably, the flux of blue light flux of blue light (specifically464 nm). Furthermore, “blue light”, referred to as specifically 464 nmlight, is meant to be interpreted to be broad spectrum blue light with aconcentration (spectral peak) at approximately 464 nm.

Also note that a lighting system with a shorter range of 3500-5000K forexample can still satisfy the requirements to coordinate circadianrhythms by regulating output of blue light (specifically the flux of 464nm light). It is within the scope of the invention that a lightingdevice comprising at least three lighting elements of characteristicchromaticity illustrated in FIGS. 13A-14B may be limited to the range of3000-6000K for example based on the balance of lighting elements in thefixture. Furthermore, a lighting device comprising at least threelighting elements of the characteristic chromaticity illustrated inFIGS. 13A-14B where each lighting device outputs at any flux level iswithin the scope of the present invention.

In one example, the circadian rhythm of a subject is regulated oraffected by artificial light where the flux of blue light (specifically464 nm) is adjusted through changes in color temperature, brightness, orboth. This example teaches that even warm white light contains aquantity of blue light which can influence a circadian response, andthat light of a constant color temperature can be modulated in intensityto induce a circadian response.

It should be noted that because the prior art does not take into accountthe flux of light in the blue region (specifically 464 nm) in whitelight control mechanisms, methods, and systems, it is possible thatprescriptive efforts to regulate a subject's circadian rhythm can haveundesirable results since all white light contains blue light. Becauseof this, simple modulation of color temperature alone is not adequate toaffect a desired circadian response.

Note the fact that users may want to adjust lighting to emulate verywarm, dimmed incandescent lighting with a characteristic colortemperature of 1800-2400K. This characteristic color temperature alsocontains a very small fraction of irradiance in the blue region (inparticular the 464 nm wavelength) compared to light in the 5000-6500Kregion. A lighting system of fixtures capable of producing light in the1800-2400K region offers the user more options to coordinate lighting insuch a way that the circadian rhythm is not disrupted by blue light.

A system is disclosed for artificially generating sunlight in accordancewith a daytime locus using spectral characteristics that resemblessunlight (including other variations of daytime sunlight such as diffuselighting, e.g., cloudless, partially cloudy, overcast, foggy, rainy,snowy, etc.). The system automatically controls at least one lightingfixture substantially along a daytime locus (e.g., white light of colortemperature from 1800K to 6500K) to generate the artificial sunlight.

A method is disclosed for artificially generating sunlight in accordancewith a daytime locus using spectral characteristics that resemblessunlight (including other variations of daytime sunlight such as diffuselighting, e.g., cloudless, partially cloudy, overcast, foggy, rainy,etc.). The method comprises: providing a plurality of channels oflighting elements (e.g., at least three channels); activating theplurality of channels to generate a composite light mixture; detectingthe composite light mixture; and controlling the plurality of channelsof lighting elements based on the detected composite light mixture togenerate artificial sunlight mixture (e.g., white light of colortemperature from 1800K to 6500K) along the daytime locus.

An artificial sunlight system is disclosed wherein the system comprisesa lighting fixture whose light output is automatically controlled toreduce the effects of, or treat, one of the group of circadian rhythmdisorders, shift work dysfunction and seasonal affective disorder byoperating along a daytime locus (e.g., white light of color temperaturefrom 1800K to 6500K) to provide compensating artificial sunlight.

A method is disclosed for artificially generating sunlight in accordancewith a daytime locus (e.g., white light of color temperature from 1800Kto 6500K) using spectral characteristics that resembles sunlight(including other variations of daytime sunlight such as diffuselighting, e.g., cloudless, partially cloudy, overcast, foggy, rainy,etc.). The method comprises: providing a plurality of channels oflighting elements; activating the plurality of channels to generate acomposite light mixture; detecting the composite light mixture; andcontrolling the plurality of channels of lighting elements based on thedetected composite light mixture to generate artificial sunlight alongthe daytime locus for reducing the effects of, or treating, one of thegroup of circadian rhythm disorders, shift work dysfunction and seasonalaffective disorder by operating along the daytime locus to providecompensating artificial sunlight.

A system for artificially generating sunlight in accordance with adaytime locus (e.g., white light of color temperature from 1800K to6500K) using spectral characteristics that resembles sunlight (includingother variations of daytime sunlight such as diffuse lighting, e.g.,cloudless, partially cloudy, overcast, foggy, rainy, snowy, etc.). Thesystem automatically controls at least one lighting fixturesubstantially along the daytime locus to generate the artificialsunlight wherein the system automatically changes brightness levels andcolor levels of a plurality of lighting element channels within the atleast one lighting fixture that generates broad spectrum white light ofcolor temperatures from 1800K to 6500K in accordance with auser-selected input. Furthermore, the system controls a total flux ofblue light (e.g., 464 nm) from a relative level of 1 to 100% of amaximum blue light flux within the broad spectrum white light.

A method is disclosed for artificially generating sunlight in accordancewith a daytime locus (e.g., white light of color temperature from 1800Kto 6500K) using spectral characteristics that resembles sunlight(including other variations of daytime sunlight such as diffuselighting, e.g., cloudless, partially cloudy, overcast, foggy, rainy,snowy, etc.). The method comprises: providing a plurality of channels oflighting elements (e.g., at least three channels); activating theplurality of channels to generate a composite light mixture; detectingthe composite light mixture; controlling a total flux of blue light(e.g., 464 nm) which can be adjusted from a relative level of 1 to 100%of a maximum blue light flux of said composite light mixture; andcontrolling said plurality of channels of lighting elements based onsaid detected composite light mixture to generate artificial sunlightalong the daytime locus having a broad spectrum white light of colortemperatures from 1800K to 6500K.

It should be understood that although the preferred color temperaturerange of operation of the present system and method is 1800K to 6500K,this is by way of example only and may vary. The important feature ofthe present invention is the artificial generation of a whole range ofsunlight scenarios (such as diffuse lighting, e.g., cloudless, partiallycloudy, overcast, foggy, rainy, snowy, etc.) which includes any type ofsunlight that occurs during the daytime using direct lighting. Thus, itis within the broadest scope of the present invention to include theartificial generation of all kinds of sunlight, including diffuselighting (e.g., diffuse UV radiation) via the system/method of thepresent invention.

In addition, the phrase “daylight locus” as used throughout thisSpecification is close in proximity to the Planckian Blackbody Curve.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The invention will be described in conjunction with the followingdrawings in which like reference numerals designate like elements andwherein:

FIG. 1A shows a blackbody curve on a 1931 CIE XY chromaticity diagram,depicting the chromatic regions over which the present inventionoperates;

FIG. 1B depicts the chromaticity change of the sunlight as the sunprogresses through the day;

FIG. 2 illustrates four points on an XY chromaticity diagramcorresponding to Kelvin scale-correlated color temperatures of 6500K,5400K, 4200K and 3200K;

FIG. 3 is an enlargement of the XY chromaticity diagram of FIG. 2corresponding to the Kelvin scale-correlated color temperatures of6500K, 5400K, 4200K and 3200K;

FIG. 4 depicts an initial condition of chromaticity x, y coordinates forexemplary lighting elements;

FIG. 5 depicts the chromaticity x,y coordinates for the exemplarylighting elements of FIG. 4 but at after 50,000 hours;

FIG. 6 depicts the relationship between the excitation and emissionspectrum of the exemplary lighting elements, showing the spectrum atinitial conditions and at 50,000 hours;

FIG. 7 depicts the angular relationship between the sun and the earth,as well as the corresponding change of path length traveled bylightwaves through the atmosphere layer;

FIG. 8 is an equation relating air mass to the zenith angle, φ_(z);

FIG. 9 depicts the changes in the spectral distribution of sunlight withair mass;

FIG. 10 is an exploded view of an exemplary lighting element of thepresent invention;

FIG. 11 is a side view of the lighting element of FIG. 10;

FIG. 12 is an exploded view of an alternative lighting element of thepresent invention;

FIG. 13A depicts three exemplary boundary boxes of lighting elementsthat can be used in the present invention to generate a color space;

FIG. 13B depicts an exemplary color space that can be generated usingthe three exemplary boundary boxes of lighting elements of FIG. 13A;

FIG. 14A depicts four exemplary boundary boxes of lighting elements thatcan be used in the present invention to generate another color space;

FIG. 14B depicts an exemplary color space that can be generated usingthe four exemplary boundary boxes of lighting elements of FIG. 14A;

FIG. 15 comprises a block diagram of a portion of the system of thepresent invention wherein a controller receives optical sensor outputsfor controlling lighting element operation;

FIG. 16 comprises a block diagram of the system of FIG. 15 but includingamplifier stages prior to the lighting elements;

FIG. 17 depicts the consolidation of the lighting elements into one ormore devices, such as multi-channel amplifiers or multi-channel drivers;

FIG. 18 depicts multiplexed devices, such as lighting elements, sensors,amplifiers, as well as other devices combined on a common digital bus;

FIG. 19 shows the use of multiple arrays or collections of deviceswithin common spatial regions which are combined on a common digitalbus;

FIG. 20 is flow diagram of the sensor activation sequence;

FIG. 21 is an amplitude vs. time plot for three groups (by way ofexample only) of lighting elements in close spatial proximity whereineach group is activated sequentially in time during calibration;

FIG. 22 depicts the sensor output voltages that monitor each lightingelement in each group when they are activated for calibration;

FIG. 23 is a chart of the recorded sensor voltages for each element ineach group during calibration;

FIG. 24 is a block diagram of a light fixture control system of thepresent invention using a non-serial network (e.g., Ethernet);

FIG. 25 is a block diagram of a light fixture control system as shown inFIG. 25 but including light sensor and user controls;

FIG. 26 is a block diagram of a light fixture control system as shown inFIG. 26 but including an extended reach via the use of network adapters;

FIG. 27 is a plot of correlated color temperature vs. time of day usedin the present invention for controlling one or more light fixtures;

FIG. 28 is a plot showing how light fixture brightness may be altered bythe present invention during a 24 hour period;

FIG. 29 is an alternative plot showing, brightness, color temperature,and time being assigned graphically using an interface consisting ofsliders and zones;

FIG. 30 depicts a user interface for controlling the system of thepresent invention;

FIG. 31 shows a further variation of the system of the present inventionwhich permits remote control of the system via a cellular phone, PDA,notebook computer, etc.;

FIG. 32 shows exemplary user interface applications for use on theremote devices for controlling the system of the present invention;

FIG. 33 is a block diagram depicting how a desktop computer can be usedto interface with a lighting control network of the present invention;

FIG. 34 depicts three exemplary user control panels within a graphicaluser interface;

FIG. 35 depicts a transimpedance amplifier circuit which is used toconvert current values from the light sensors into voltages;

FIG. 36 depicts a transimpedance amplifier circuit which can convertmultiple sensor input currents into voltages;

FIG. 37 is a chart relating the effective range the transimpedanceamplifier is effective for a given resistor setting; and

FIG. 38 is a chart depicting how the system/method of the presentinvention may be used to acclimate a subject to a 36-hour day, ratherthan a 24-hour day.

DETAILED DESCRIPTION

Although there are many uses of the invention of the presentapplication, one of the most important is circadian rhythm applications.Circadian rhythm disturbances may be circadian rhythm imbalances,hormonal imbalances activated by exposure to light, shift workcondition, or seasonal affective disorder. In particular, the inventionof the present application comprises a lighting system which can treatand prevent circadian rhythm disorders. Also included within thebroadest aspect of this invention are other applications whereprevention of shift work dysfunction, seasonal affective disorder, andcircadian rhythm disorders is mission critical, such as militaryapplications (including navy vessels) and manned aerospace applications.Furthermore, the utility of the present invention can be invoked ingeographic locations where the sky is often overcast or sunlight isscarce. The invention would equally apply to travelers since jet lag isrelated to the circadian rhythm. This application has customers in thepassenger rail industry, airline industry, and hospitality industry.

Furthermore, the benefits of low glare, high CRI (Color Rendering Index)daylight white lighting extend beyond health benefits. Studies haveshown increases in productivity, retail sales, and classroom performancein daylight-lit spaces. For these reasons, the present invention canprovide greater efficiencies in retail applications, office andcommercial applications, and education/higher education applications. Infact, retailers may find it useful to display their products in theoptimal type of light, to further enhance every bit of the shoppingexperience. Restaurants which serve patrons from morning through theevening often use several circuits of incandescent lights or dimmers tochange the lighting conditions throughout the day. A lighting system,such as the present invention, that keeps patrons comfortable atbreakfast while being able to deliver a warm intimate atmosphere atcocktail hour is particularly appealing in this regard.

In FIG. 1A, the blackbody curve 200 (also referred to as the “daylightlocus”) is plotted on a 1931 CIE (Commission Internationale del'Eclairage) XY chromaticity diagram 201, illustrating the chromaticregions through which the invention operates. In FIG. 2, four points210, 211, 212, and 213 are represented on a similar XY chromaticitydiagram 209 on the blackbody curve 208 corresponding to the Kelvin scalecorrelated color temperatures (CCT) of 6500K, 5400K, 4200K, and 3200K—analternate method of specifying regions on the chromaticity diagram.

FIG. 1B depicts the relative positions on the XY chromaticity diagramwhere direct sunlight may be characterized by measure of air massestraversed at ground level. Reference point 204 indicates the point wheredirect sunlight with clear skies at an air mass of 1.0 would bepositioned on the CIE chromaticity diagram, which is accepted to beapproximately 6500K by measure of correlated color temperature by thoseskilled in the art. Reference point 205 corresponds to an air massof >1, while reference points 207 and 208 correspond to higher airmasses ≧5 and ≧10, respectively. This bounding box encloses theblackbody curve along which the sun's chromaticity coordinates vary from1-37 air masses. Special considerations are given for spectral shiftsduring the lifetime of the lighting fixture, ensuring that after thelighting elements decay, the bounding box will sufficiently cover thechromaticity points corresponding to the sun's spectral distributionbetween air masses 1 and 37.

For the purposes of describing white light, it is useful to truncate theCIE 1931 chromaticity diagram to the region of interest. The diagram inFIG. 3 shows correlated color temperature in degrees Kelvin at points214 (6500K), 215 (5400K), 216 (4200K), and 217 (3200K) in a similarfashion as FIG. 2.

Bounding boxes 230, commonly referred to as “bins” by those versed inthe art, are represented on an x-y chromaticity diagram 231. A boundingbox, or bin, can be described by four coordinate points on thechromaticity diagram. A bin describes a sampling of lighting elementspossessing a distribution of chromaticity characteristics defined withinthe bounding box, and various nomenclature systems may be used todescribe individual bounding boxes or bins, a term used by thosepracticed in the art. A sampling of many lighting element's chromaticitycharacteristics can be plotted on a chromaticity coordinate system andarranged into bins, where the chromaticity characteristics aredetermined by optical testing. The dimensions of the bin (area on thex-y chromaticity chart) describes the variation in the spectraldistribution for a given sample of similar lighting elements.

Any lighting element is subject to various modes of optical decay,dissipation, or degradation. These modes of decay may be related tobrightness decreases (lumen decay) or spectral shifts throughout thelifetime of the lighting element. Spectral shifts may also occur due tothe thermal state or variations in the operating voltage of a lightingelement. Many solid state lighting elements produce broad spectrum lightby down converting high frequency monochromatic light (herein referredto as excitation source) into broad spectrum lower frequency emissionusing specialized downconverters or lumiphors. These downconverters mayconsist of phosphors, quantum dots, organic semiconducting materials,photonic crystals, nano photonic crystals, and other photonic crystals.These various downconverters are subject to modes of degradation ordecay, such as quantum efficiency decay, spectral shifting, thermaldecay, oxidation, excitation peak shifts, and emission shift to name afew.

Four lighting element at points 231, 232, 233, and 234 possessing uniquespecific chromaticity coordinates are represented at an initialcondition in FIG. 4. In such initial condition, the thermal stateattribute, forward voltage attribute, lifetime attribute, degradationstate, or a combination of any of these attributes is withinpredetermined limits. It should be noted that the thermal stateattribute describes the junction temperature, influenced by ambienttemperature, lighting fixture temperature, or increased temperature dueto operation. The lifetime attribute describes the total activeoperating time, and the degradation state describes the condition of thelighting element due to events such as oxidation, over heating, oroperating time brightness decay.

In a second condition, one or a combination of several operatingattributes has changed from the initial condition. Changing one or acombination of these attributes causes a change in the lightingelement's optical chromaticity coordinate, shown in FIG. 5 for points235, 236, 237, and 238. For example, in the initial condition describedby FIG. 4, the lighting elements have not been operated and are at alifetime of 0 hours. In the second condition described by FIG. 5, thelighting elements have been operated for 50,000 hours and possessdifferent chromaticity x, y coordinates.

In the case of degradation due to operating time, the relationshipbetween the excitation and emission spectrum is described by FIG. 6. Thespectral characteristics of a lighting element at zero operation hours,or an initial condition, is represented as a solid line 219 on awavelength scale 218. The spectral characteristics of a lighting elementat 50,000 operating hours is represented as a dashed, discontinuous line221 on the same wavelength scale 218.

In an initial condition where lighting elements are at an operatinglifetime of 0 hours, the excitation intensity is at a higher level 220than the excitation intensity in a degraded state, 222. Similarly, thebroad band converted light goes from an initial high intensity 219 to alower intensity in a degraded state 221.

FIG. 7 describes the angular relationship between the sun 240 and theearth 241, along with the corresponding change of path length 244traveled through the atmosphere layer 242. As the sun's angle, here inreferred to as zenith angle, φ_(z), 243 changes with respect to a fixedpoint on the earth's surface 241, the path length 244, herein referredto as air mass, of the light through the atmosphere layer changes. Theboundaries of the zenith angle 243 correspond to the horizons observedfrom the ground, and are −90° and +90°. This path length is commonlymeasured in the unit of air masses. For example, a zenith angle 243 of0° between the sun and earth's surface corresponds to an air mass of1.0, while a zenith angle 243 of 90° corresponds to an air mass of 38.

FIG. 8 is an expression which relates air mass 245 to any given zenithangle 246 of the sun. This zenith angle 246 can further be related tothe geographic location on the earth's surface, the time of day, and thedate.

FIG. 9 describes the changes in the spectral distribution of sunlightwith air mass. It is shown that for a high air mass 246 of 10, asignificant decrease in wavelengths 450-600 is present relative to anair mass 247 of 1, as well as a decrease in total irradiance relative toan air mass 247 of 1.

FIG. 10 provides an exemplary lighting fixture 319 of the presentinvention. The lighting fixture 319 comprises solid state lightingelements 250, thermal dissipation components 251, logic and powerconversion components 252, reflector 253 and optical components 257,spectrally unique sensors 258, heat sink or heat pipe 254, internalinterconnects 255, and other structural housing features 256. Where,components are assembled together into unified device consisting of afixture body 270, power interconnect 271, and optical aperture emittingillumination 272 illustrated in FIG. 11. In this embodiment, thecomponents are assembled into a round compact fixture suitable forproviding targeted light, recessing into a ceiling, or replacing acommon recessed flood light. By way of example only, the sensors 258 maybe formed on a single wafer or cell as shown in FIG. 10.

Similarly, these key components may be arranged in an alternate fashion.Another such lighting fixture embodiment 319A is represented in FIG. 12,where lighting elements 260, optical components 261, heat sink 262 andthermal dissipation components 263, and a housing 264 are arranged in analternate form. In this embodiment 319A, this alternate form is a linearfixture, suitable for lighting larger areas using a single fixture.Furthermore, in this configuration, the sensors 258 a are distributed,as shown in FIG. 12.

In lighting fixtures 319/319A containing a plurality of lightingelements 250/250A, two elements possessing unique spectralcharacteristics can be placed in close proximity where the light emittedtravels into a cavity and is reflected off of one or more surfaces,mixing the light.

FIG. 13A shows three exemplary bounding boxes 275, 276 and 277 whoselighting elements have unique spectral distributions and which, whenmixed properly in the present invention, combine to generate a colorspace, e.g., color space 280 shown in FIG. 13B. By way of example only,the present invention may comprise three channels of lighting elementsdefined as follows:

Channel 1 (cool white) comprising bounding box on x,y chromaticitydiagram with four points given by (x,y). lighting elements comprisingchannel 1 possess chromaticity characteristics falling within thebounding box 275:

-   -   Point one having x,y chromaticity coordinates of 0.30, 0.33;    -   Point two having x,y chromaticity coordinates of 0.35, 0.37;    -   Point three having x,y chromaticity coordinates of 0.35, 0.34;        and    -   Point four having x,y chromaticity coordinates of 0.31, 0.31.

Channel 2 (warm white) comprising bounding box on x,y chromaticitydiagram with four points given by (x,y). lighting elements comprisingchannel 2 possess chromaticity characteristics falling within thebounding box 276:

-   -   Point one having x,y chromaticity coordinates of 0.37, 0.39;    -   Point two having x,y chromaticity coordinates of 0.48, 0.43;    -   Point three having x,y chromaticity coordinates of 0.46, 0.39;        and    -   Point four having x,y chromaticity coordinates of 0.36, 0.35.

Channel 3 (amber) 277: comprising bounding box on x,y chromaticitydiagram with four points given by (x,y). lighting elements comprisingchannel 3 possess chromaticity characteristics falling within thebounding box

-   -   Point one having x,y chromaticity coordinates of 0.54, 0.42;    -   Point two having x,y chromaticity coordinates of 0.55, 0.45;    -   Point three having x,y chromaticity coordinates of 0.60, 0.40;        and    -   Point four having x,y chromaticity coordinates of 0.57, 0.40.

FIG. 14A shows four exemplary bounding boxes 282, 283, 284 and 285 whoselighting elements have unique spectral distributions and which, whenmixed properly in the present invention, combine to generate a colorspace, e.g., color space 286 shown in FIG. 14B. By way of example only,the present invention may comprise four channels of lighting elementsdefined as follows:

Channel 1 (very cool white) comprising bounding box on x,y chromaticitydiagram with four points given by (x,y). LED emitters comprising channelone possess chromaticity characteristics falling within the bounding box282:

-   -   Point one having x,y chromaticity coordinates of 0.30, 0.33;    -   Point two having x,y chromaticity coordinates of 0.35, 0.37;    -   Point three having x,y chromaticity coordinates of 0.35, 0.34;        and    -   Point four having x,y chromaticity coordinates of 0.31, 0.31.

Channel 2 (neutral) comprising bounding box on x,y chromaticity diagramwith four points given by (x,y). lighting elements comprising channelone possess chromaticity characteristics falling within the bounding box283:

-   -   Point one having x,y chromaticity coordinates of 0.35, 0.37;    -   Point two having x,y chromaticity coordinates of 0.41, 0.41;    -   Point three having x,y chromaticity coordinates of 0.40, 0.37;        and    -   Point four having x,y chromaticity coordinates of 0.35, 0.34.

Channel 3 (warm white) comprising bounding box on x,y chromaticitydiagram with four points given by (x,y). lighting elements comprisingchannel one possess chromaticity characteristics falling within thebounding box 284:

-   -   Point one having x,y chromaticity coordinates of 0.41, 0.41;    -   Point two having x,y chromaticity coordinates of 0.48, 0.43;    -   Point three having x,y chromaticity coordinates of 0.46, 0.39;        and    -   Point four having x,y chromaticity coordinates of 0.40, 0.37.

Channel 4 (amber) comprising bounding box on x,y chromaticity diagramwith four points given by (x,y). lighting elements comprising channelone possess chromaticity characteristics falling within the bounding box285:

-   -   Point one having x,y chromaticity coordinates of 0.54, 0.42;    -   Point two having x,y chromaticity coordinates of 0.55, 0.45;    -   Point three having x,y chromaticity coordinates of 0.60, 0.40;        and    -   Point four having x,y chromaticity coordinates of 0.57, 0.40.

As mentioned previously, one of the unique aspects of the presentinvention is the ability to control lighting devices, and morespecifically, (as will be discussed in detail below), controlling thebrightness levels and the color levels of a plurality of lightingelement channels. And as also mentioned earlier, this control iseffected by permitting inputs to be made (either manually orautomatically):

1) dimming level;

2) dimming level and color temperature level;

3) time of day;

4) time zone;

5) geographic location;

6) desired circadian response;

7) present activity (e.g., sleep, reading, working, studying, eating,resting, etc.); and

8) angle of sun.

A ninth input is the flux of color light, i.e., being able to controlthe total flux of a specific color light from a relative level of 1-100%the maximum color flux of the lighting fixture through control of eachindividual lighting element.

This is especially important for the flux of blue light (viz., 464 nm).It should be noted that a lighting system with a shorter range of3500-5000K for example can still satisfy the requirements to coordinatecircadian rhythms by regulating output of blue light (specifically theflux of 464 nm light). It is within the scope of the invention that alighting device comprising at least three lighting elements ofcharacteristic chromaticity illustrated in FIGS. 13A-14B may be limitedto the range of 3000-6000K for example based on the balance of lightingelements in the fixture. Furthermore, a lighting device comprising atleast three lighting elements of the characteristic chromaticityillustrated in FIGS. 13A-14B where each lighting device outputs at anyflux level is within the scope of the present invention.

In one example, the circadian rhythm of a subject is regulated oraffected by artificial light where the flux of blue light (specifically464 nm) is adjusted through changes in color temperature, brightness, orboth. This example teaches that even warm white light contains aquantity of blue light which can influence a circadian response, andthat light of a constant color temperature can be modulated in intensityto induce a circadian response.

The present invention implements a prescriptive control of the bluelight component of the overall white light emission. By way of exampleonly, a combination of at least three lighting fixtures can becontrolled whereby the total flux of blue light can be adjusted from arelative level of 1-100% the maximum blue flux of the lighting devicethrough control of each individual lighting element. Therefore, forexample, where three lighting fixtures emit white light at 20 lux, 200lux and 2000 lux, respectively, the blue light component for eachfixture can be controlled at a 25% relative level, namely, 5 lux, 50 luxand 500 lux, respectively.

As shown in FIG. 15, a controller 299 executes operations within afixture 319 by employing a closed loop feedback mechanism incorporatingat least two spectrally unique sensors 300 and at least one lightingelement 250/260 using at least three channels 301. Means of externalinput 302 allows for the fixture to be dimmed or for its colorconditions to be changed by applying a modulated duty cycle or byapplying a pulse width modulation (PWM) signal to the channels or groupsof lighting elements. In the case of high power LEDs suited for generalillumination, other components 303 such as amplifiers or drivers arenecessary to amplify the PWM signals produced by the controller, howeverfor illustration purposes, these components will be summarized as above.Elements enclosed by the dashed line 319 are components within a singlefixture.

Similarly, the lighting elements 308 can be grouped or consolidated intoone or more devices 305 such as a multi channel amplifier, multi channeldriver, or other controller coupled with an analog to digital convertercircuit before coupling with the controller 309. To those known in theart, it is apparent that there are several ways of multiplexing thesechannels, and illustrated within are a few common examples. Inparticular, FIG. 16 shows the configuration of FIG. 15 using dedicatedamplifiers 303 for the three channels 301. Alternatively, amulti-channel amplifier 305 can be used as shown in FIG. 17.

As shown in FIG. 18, multiplexed devices such as lighting elements,sensors, amplifiers, and other devices may be combined on a commondigital bus 310 as a means of interconnecting with a central controllerusing a variety of analog to digital converters, drivers, orcontrollers. A collection of sensors and lighting elements within closeproximity can form an array 307 or individual closed loop when the saiddevices are connected to a common bus. The analog to digital convertercircuit in FIG. 18 may comprise a microcontroller device capable ofaccepting a plurality of analog inputs and combining them on a commonconnection such as a digital interface, an I2C interface, or a serialinterface.

For some types of optical sensors such as photodiodes, a transimpedanceamplifier may be necessary to convert current to voltage for thecontroller to process feedback data. FIG. 16 depicts sensors connectedto singular transimpedance amps 500 which consist of a single currentinput and a single voltage output. FIGS. 17, 18, & 19 depict sensorswhich are connected to a multi-channel transimpedance amplifier 507which accepts multiple current inputs from sensors and outputs multiplevoltages to the controller. To those skilled in the art, it is apparentthat this multi-channel transimpedance amplifier can be combined with orinterfaced to an analog to digital converter to combine a plurality ofvoltage signals to a single digital interface such as I2C. Thisarrangement has not been explicitly illustrated.

FIG. 19 shows that multiple arrays or collections of devices withincommon spatial regions can be combined on a common digital bus 315 andcontroller 318, forming multiple closed feedback loops 316, 317 within asingular fixture represented by a bounding dashed line 319 (or 319A).

FIG. 20 shows the sensor activation sequence. Following theinitialization step 320, channels 1, 2, and 3 are activated during steps321, 323, 325, respectively, in sequence and the corresponding sensordata are recorded during recordation steps 322, 324 and 326. From datagathered, the color match function is executed at step 327 and theresult is sent to the controller at step 328 to accurately operate thefixture at the correct color. Basically, the color match function (CMF)involves driving the lighting elements to the calibration point of thesensors. This can be achieved in various ways from manual changes toautomated methods or a combination of both.

As mentioned previously, three unique spectral sensors (A, B and X) arein close proximity to the at least three channels 301 comprising aplurality of lighting elements (250). However, it should be understoodthat the number of sensors is not limited to three (hence, the sequence,A, B and X, with indicating an infinite number of sensors). In fact, itis within the broadest scope of the invention to include at least twosensors. Similarly, it should be understood that the number of channelsis not limited to three (hence the sequence of 1, 2, μ). In fact, it iswithin the broadest scope of the invention to include at least threechannels.

In this embodiment, a first group or channel of lighting elements isactivated 330, illustrated by the FIG. 21 output chart with time on thex axis 331 and amplitude on the y axis 332. At this time, acorresponding set of inputs from the sensors is recorded, illustrated byvoltages 333, 334, and 335 on the input chart in FIG. 23. A second groupor channel of lighting elements is then activated 336 and another set ofinputs 337 are recorded from the sensors. This process continues untilall X channels are activated.

FIG. 23 illustrates the data available to the fixture upon completion ofthe calibration sequence described by FIGS. 22-23. Columns 341, 342,343, and 344, represent the data obtained from the short interval inwhich a single lighting element or collection of common elements isilluminated at the start up sequence. Column 344 represents valuescorresponding to the unique inputs obtained from the sensors afterapplying a balanced duty cycle to each lighting element, or illuminatingeach element to balanced intensities. Values 345 are the initialcondition (lifetime=0 hours) balanced duty cycle voltages obtained fromthe sensors with a new lighting element or elements. This illustrateddata is used by the controller and algorithms to illuminate a collectionof lighting elements where the additive output corresponds to predetermined conditions.

As shown in FIG. 24, a serially linked digital network 350 (e.g., RS-485or RS-232) may be used to control lighting elements 353 and a centralcontrol unit 351. This network can establish a strictly one way or twoway communication between devices. In this embodiment, a typicallighting control network interfaces with another non-serial network suchas a common Ethernet network 352 for accessing advanced features,configurations, and diagnostic information. The serially linked digitalnetwork 350 may use a digital protocol such as I2C, a serial protocolsuch as RS-485, RS-232, or a wireless protocol such as Zigbee or otherRF signals.

FIG. 25 shows that such control networks can also incorporate otherelements common to lighting systems such as light sensors 354 and usercontrols 355 such as switches. These devices are identified on thenetwork as any other device with an address and defined input and oroutput channels, operating on a common communication protocol.

As shown in FIG. 26, this communication protocol may be transmittedacross other common networks such as Ethernet or wireless networks usingnetwork adapters 360 to extend the reach of a control network or tosimplify interconnection of single devices 361, 362 or groups of devices363, 364. In this embodiment, a wired Ethernet network is illustrated inwhich adapters are employed to extend the reach of devices on thecontrol network.

With a communications network in place linking multiple lightingfixtures, several time-color profiles can be assigned to one or more ofthese fixtures. In one embodiment, a simple schedule described in FIG.27 is assigned to a group of lighting fixtures, in which the horizontalx axis 380 represents the time of day from 0 to 24 hours, and thevertical y axis 381 represents the correlated color temperature indegrees Kelvin. This profile gradually varies the correlated colortemperature of the lighting fixtures over a period of 24 hours,illustrated by the solid line 382. FIG. 28 describes how brightness of afixture may be changed throughout a 24 hour period where the horizontalx axis 383 represents the time of day from 0 to 24 hours, and thevertical y axis 384 represents the perceived brightness of the fixture.The profiles described in FIGS. 28-29 may be assigned independently ofone another, and only represent one embodiment of the invention.Regarding schedules (e.g., as shown in FIGS. 27-29), the time period maybe variable, corresponding to a day (e.g., 24 hours), a portion of aday, defined by the lighting device as a function of input such asintensity or dimming level, or defined by an external controller as afunction of input such as intensity or dimming level. In one embodiment,a dynamically changing brightness-color function is used in response touser input rather than a defined schedule. In this embodiment, the colortemperature of the lighting fixtures is dynamically changed in real timein response to the user defined brightness of the fixture. The resultantbehavior of this embodiment is meant to mimic the color-brightnessbehavior of an incandescent light bulb being dimmed.

It should be noted that the communication system:

-   -   may comprise methods to program cues and or schedules;    -   may be analog in nature and wherein changes in an input voltage        denote a change in cue or lighting schedule;    -   may include a digital connection comprising serialized data bits        or packets coordinating fixtures;    -   may comprise an external control device and tree structure or        daisy chain structure;    -   may comprise communication of cue changes or activation of        conditions programmed into fixtures;    -   may comprise communication of specific colorimetric or feedback        loop data;    -   may comprise a communication of pulse width modulation        parameters; or    -   may comprise a wireless mesh network exhibiting distributed        structure or top down structure.

In another embodiment described by FIG. 29, brightness, colortemperature, and time are assigned graphically using an interfaceconsisting of sliders 388, 389 and zones 390, 391, 392. Profilescontaining time dependent information on brightness and colortemperature may be saved in a digital format and modified by the user.

Settings, profiles, preferences, and other functions such as off and onmay be controlled using a push button interface installed in aninterior. FIG. 30 describes one such interface 395 where the userinteracts with the system using a collection of push buttons. Similarly,these push buttons may be arranged on a touch sensitive display devicecapable of dynamically changing to present the user with additionaloptions 396. Interactions with the control panels described in FIG. 30results in dynamic changes to the system which may include time, color,and brightness autonomous changes requiring no further input.

FIG. 31 describes an embodiment in which a handheld computing devicesuch as a phone, PDA, or notebook computer 400 makes a common connection401 with an adapter 402 in the communication network common to thelighting elements 403 and central controller 404. In this embodiment, auser is able to make changes to the lighting network affecting timedependent functions of color and brightness of the lighting fixtures.

FIG. 32 describes several user options available to a handheld computingdevice 409, where 410, 411, and 412 are three such control panels whichcan be displayed on the integrated display device in the handheldcomputing device 409. User inputs on the handheld device through controlpanels described in FIG. 32 can have a time dependent change onbrightness and color of the lighting elements in the control network.

FIG. 33 depicts how a desktop computer can be used to interface with alighting control network. In this embodiment, the central control unit421 can store settings defined by the computer device 420 through agraphical user interface where a user modifies settings affectingbrightness, color, and time of lighting characteristics produced bylighting fixtures 424 in the network using human input devices such as akeyboard 423 and mouse 422. In this embodiment, the computer isnecessary only to apply settings to the control unit 421, and in anothersuch embodiment, the computer 420 directly controls the lightingelements 424 using the control unit 421 as a network translator.

FIG. 34 describes three user control panels in the graphical userinterface. Users modify parameters in the interface using a humaninterface device such as a mouse or keyboard. Display screen 450 depictshow the spatial position of a lighting fixture 449 may be defined inrelation to a room floor plan 451 and a window 452. Display screen 453depicts a method by which the user can make a selection of lightingfixtures by drawing an enclosed shape 454 on the floor plan 455. Panel456 describes the interface using sliders 457 and zones 458 used tomodify color and brightness schedules.

FIG. 35 depicts how the present invention controls the sensor gainsetting. In particular, FIG. 35 depicts a single transimpedanceamplifier circuit unit 500 which is used to convert the current outputof a photodiode sensor 501 into a voltage 506 suitable for interfacingto a controller. This transimpedance amplifier circuit operates using aconstant reference voltage 502, an OP Amp 503, a resistor 504 (e.g., apotentiometer, MTI04C transimpedance amplifier that uses an internalvariable resistor, etc.), and a capacitor 505. The 504 resistancedetermines the input current 501 sensitivity and may be held constant orcan be changed to accommodate a wide dynamic range of input current 501.The capacitor 505 is selected to properly compensate the inputcapacitance of the photosensor. The resistor 504 may be internal to theamplifier component 500, in which case its value is fixed; it mayconsist multiple internal resistors to the component which are activatedby pins on the device, or this resister may be located external to theamplifier 500, in which case it may be variable.

FIG. 36 depicts a similar transimpedance amplifier to FIG. 35 butcomprises multiple input currents 508 and multiple output voltages 509.This multi channel transimpedance amplifier 507 operates similarly tothe amplifier described in FIG. 35, employing multiple OP amps andresistors 510 with one singular reference voltage 511.

Since the light fixture's brightness level is variable, the lightfalling on the sensor may not be within the transimpedance amplifier'scurrent threshold. This is why it is useful to change the resistor 504resistance value to properly suit the sensing range of the fixture. FIG.37 relates the light fixture's intensity given by series 517 ranging in20%-100% relative brightness to the required resistance 516 in thetransimpedance amplifier circuit necessary to resolve a voltage 515 toproperly acquire optical feedback. For example, at 100% relativebrightness, a given lighting channel's luminance may activate a givensensor, providing a current from the photodiode on the order of 1-10 μA.In order for the transimpedance amplifier to resolve this range ofcurrent, the resistance of resistor 504 must be on the order of 100KΩ.In another case, the lighting fixture is dimmed to 20%, providing only0.1 μA of current for the transimpedance amplifier 500. If resistor 504is fixed at 100KΩ, the voltage output 506 of the amplifier will be at aconstant minimum 516, providing no useful data for feedback. In thiscase, it is necessary to change the resistance of resistor 504 to ˜5 MΩto achieve sensitivity in the 0.1-0.05 μA current range.

By way of example only, one application of the system/method of thepresent invention is the generation of an enriched light at 460 nm at anirradiance of 30 μW/cm² for use in treating clinical jaundice innewborns. Approximately 60% of all newborns become clinically-jaundicedsometime during the first week of life and phototherapy is indicated tohelp the neonatal liver clear bilirubin from their blood, as recommendedby the Academy of Pediatrics.

Another exemplary application of the system/method of the presentinvention is the generation of an enriched light of 290 nm-315 nm to aidin Vitamin D production. This is an issue especially in the wintermonths as many people do not go outdoors and receive adequate sunlightexposure. This is also becoming an issue in the summer months too, asmany elderly are staying out of the sun and closing their shades to saveon energy costs. Seasonal Affective Disorder is usually treated with alight therapy of as much as 10,000 lux at 30 inches from the body for atleast 30 minutes per day. In contrast, the light box therapy usedcurrently is more focused on total lux versus the quality of the lightto match a full sunlight spectrum.

Thus, it should be understood that another exemplary application of thesystem/method of the present invention is Circadian Rhythm manipulation.For example, the present invention can implement Circadian Rhythmmanipulation for the following individuals or scenarios:

-   -   military application of training soldiers for 36-hour days;    -   weaponization (intentional disorientation of enemy combatants'        biorhythms);    -   astronauts (for off-Earth environments or unintended        return-to-Earth environments); this would include Lunar or Mars        missions, or employing the system/method at 1000 atmospheres        below the ocean surface; the color temperature may be strange to        compensate for deep space/Mars/ocean attenuation/or generally        odd locally available light;    -   other military or aerospace applications which utilize different        color spaces, e.g., conditioning Mars astronauts and training to        work in constant 1800K Mars atmosphere light while maintaining        Circadian Rhythm balance, or conditioning soldiers for 36 hour        day deployments and back to 24 hour off-duty cycles. By way of        example only, FIG. 38 depicts an exemplary schedule where the        system/method of the present invention is utilized in a        Circadian Rhythm manipulation. In particular, FIG. 38 describes        another embodiment, in which the lighting system is used to        adjust a subject to a 36-hour day, rather than a 24-hour day. In        this embodiment, cycles of variable time periods are inputted        end to end into the lighting system, beginning with a 24 hour,        525 daily schedule. The 24 hour cycles are followed by multiple        526 conditioning cycles, ranging between 24 and 36 hours,        comprising the conditioning period 526. After the subjects have        been appropriately conditioned to a 36 hour day, the deployment        period 527 begins, which consists a user-defined length in        number of cycles. In order to acclimate a subject back to a        natural 24 hour 529 daily schedule, a recovery period 529 is        defined by the user.

It should be noted that the lighting elements discussed above maycomprise chip-type light emitting diodes (LEDs), packaged LED emitters,arrays of chip type LED emitters incorporated into a single package, orcollections of packaged LED emitters attached to a common board or lightengine. These LED emitters may be coated with materials intended toconvert high frequency light into low frequency broad spectrum light,such as YAG:Ce phosphors, phosphor coatings, phosphor films, or lensescontaining phosphor dispersions. Additionally, quantum dot photoniccrystals, photonic nanocrystals, or semiconducting nanoparticles may beincorporated into lighting elements by means of coating, film, or filledlens material to convert high frequency light into lower frequencylight. By extension, lighting elements may incorporate a blend oflumiphors or conversion materials, where each component converts lightto a unique lower frequency color. More than one lumiphor may beincorporated into lighting devices where lumiphors are applied insequence to different regions of the light emitting component, analogousto sub pixels on a video display. Lighting elements may also comprisedevices employing organic semiconducting materials, such as organiclight emitting diodes (OLEDS), or phosphorescent materials which emiteither white or narrow band light in specific regions in the spectrum.

It should be further noted that intensity of channels or groups oflighting elements may be changed by pulse width modulation, currentmodulation, or other means of duty cycle modulation.

The sensors identified in FIGS. 16-24 may comprise charge coupleddevices (CCD), ceramic metal oxide sensors (CMOS), phototransistors, orphotodiodes. Each sensor may be an assembly or collection of multiplesuch devices employing visible filters or neutral density filters at theoptical aperture of the sensors. Additionally, this sensor may be a chiptype device incorporating multiple such sensors and color filters in asingle package. Arrays packaged in this manner are often referred to as“color sensors” and may incorporate a means of changing gain settings tomodify the luminous flux-output characteristics of the device via pinjumper settings. Sensors, sensor arrays, or sensor assembliescommunicate with the controller via an analog or digital interface. Thesensor or sensors may employ a transimpedance circuit to convertdiscreet current outputs to voltages and an integrated analog to digitalconverter circuit to combine the outputs of multiple sensors on a singledigital or serial interface. Example components include:

a. ADJD-S313-QR999 digital RGB 7 bit color sensor from AvagoTechnologies;

b. HDJD-S722-QR999 analog RGB color sensor from Avago Technologies;

c. Hamamatsu S10170 3—channel photodiode;

d. TAOS TCS230 Light to Frequency converter

It should be further noted that it is within the broadest scope of thepresent invention to include various types of optical sensors andoptical sensor output formats. For example, the optical sensors of thepresent invention may include analog optical sensors that outputvoltages or digital sensors that output data and/or frequency. Thus,optical sensors that output chromaticity coordinates as opposed tovoltage, frequency or other output formats (e.g., other data) are allwithin the broadest scope of the invention. This also includes varioussensor processing mechanisms such as voltage/frequency/current signalsthat are representative of optical data that can be correlated withknown optical data (e.g., via look-up tables or other correlationmethods).

It should also be noted that although the preferred system and method ofthe present invention utilize feedback control, it is within thebroadest scope of the present invention to include a light fixturesystem or light fixture method that uses no feedback control toartificially generate the daylight locus.

It should be further noted that it is within the broadest scope of thepresent invention to include the use of the more recent CIE 1960chromaticity diagram, in addition to the CIE 1931 chromaticity diagrammentioned previously, with regard to the system/method operation of thepresent invention.

While the invention has been described in detail and with reference tospecific examples thereof, it will be apparent to one skilled in the artthat various changes and modifications can be made therein withoutdeparting from the spirit and scope thereof.

The various embodiments described above can be combined to providefurther embodiments. U.S. Pat. No. 8,436,556, issued May 7, 2013 andU.S. Provisional Application No. 61/249,858, filed Oct. 8, 2009, areincorporated herein by reference, in their entirety. Aspects of theembodiments can be modified, if necessary to employ concepts of thevarious patents, applications and publications to provide yet furtherembodiments.

These and other changes can be made to the embodiments in light of theabove-detailed description. In general, in the following claims, theterms used should not be construed to limit the claims to the specificembodiments disclosed in the specification and the claims, but should beconstrued to include all possible embodiments along with the full scopeof equivalents to which such claims are entitled. Accordingly, theclaims are not limited by the disclosure.

The invention claimed is:
 1. A system to control a plurality of channelsof lighting elements to generate artificial sunlight with spectralcharacteristics that resemble natural sunlight, the system comprising: acontroller communicatively coupled to receive input signals, to receivesignals from a number of light sensors, and to control the plurality ofchannels of lighting elements, the controller operable to: sequentiallyindividually activate each of the channels of lighting elements, receivesignals from the light sensors, the respective signals representative ofdetected light for each of the channels of lighting elements;automatically create a calibrated setpoint for each of the channels oflighting elements based at least in part on the respective signalsgenerated for the respective channel of lighting elements by the lightsensors; automatically create respective drive signals for each of thechannels of lighting elements based at least in part on the calibratedsetpoint for the respective channel of lighting element and based atleast in part on the received input signals; and automatically providethe respective drive signals to the channels of lighting elements toautomatically vary a brightness level and a color level of therespective channels of lighting elements to produce a composite lightalong at least a portion of a daylight locus.
 2. The system of claim 1wherein the input signals are representative of at least oneuser-selected input.
 3. The system of claim 2 wherein the user-selectedinput indicates a current activity of the user, and the respective drivesignals automatically vary the brightness level and the color level forthe respective channels of lighting element to produce the compositelight along at least a portion of the daylight locus that corresponds tothe current activity of the user.
 4. The system of claim 2 wherein theuser-selected input indicates a desired sunlight scenario, the desiredsunlight scenario which is one of cloudless, partially cloudy, overcast,foggy, rainy, and snowy, and the respective drive signals automaticallyvary the brightness level and the color level for the respectivechannels of lighting element to produce the composite light along atleast a portion of the daylight locus that corresponds to the desiredsunlight scenario.
 5. The system of claim 2 wherein the user-selectedinput indicates a desired one of at least two different color-timeprofiles, each of the at least two different color-time profiles specifyvalues for one or more of brightness and color temperature versus time,and the respective drive signals automatically vary the brightness leveland the color level for the respective channels of lighting element toproduce the composite light along at least a portion of the daylightlocus that corresponds to the values specified by the desired one of theat least two different color-time profiles for a current time.
 6. Thesystem of claim 2 wherein the user-selected input indicates a geographiclocation, and the respective drive signals automatically vary thebrightness level and the color level for the respective channels oflighting element to produce the composite light along at least a portionof the daylight locus that corresponds to lighting conditions that existat the geographic location.
 7. The system of claim 1 wherein the inputsignals are representative of at least one defined schedule.
 8. Thesystem of claim 1 wherein the plurality of channels of lighting elementscomprise a plurality of arrays combined on a common digital bus, each ofthe plurality of arrays comprising at least three of the channels oflighting elements and at least two of the at least two light sensorsgrouped within a common spatial region, the controller which providesvia the common digital bus respective drive signals to the at leastthree channels of lighting element channel of each of the plurality ofarrays based at least in part on the respective signals representativeof the composite light detected by the at least two light sensors ofsuch array to form a plurality of closed feedback loops.
 9. The systemof claim 1 wherein the plurality of channels of lighting elements areselectively operable to generate broad spectrum white light.
 10. Thesystem of claim 1 wherein the controller controls a total flux of bluelight from a relative level of 1% to 100% of a maximum blue light fluxwithin white light produced by the lighting elements.
 11. The system ofclaim 1 wherein the plurality of channels of lighting elements areselectively operable to generate broad spectrum white light of colortemperatures higher than 3000K and lower than 5000k.
 12. The system ofclaim 1 wherein the plurality of channels of lighting elements areselectively operable to generate broad spectrum white light of colortemperatures higher than 1800K and lower than 6500K.
 13. A system tocontrol a plurality of channels of lighting elements to generateartificial sunlight with spectral characteristics that resemble naturalsunlight, the system comprising: a controller communicatively coupled toreceive signals from a number of light sensors representative of atleast one characteristic of a composite light emitted by the lightingelements, and communicatively coupled to control the channels oflighting elements, the controller operable to: receive a user-selectedinput that specifies an adjustment for a time-color profile thatspecifies values of one or more of brightness and color temperatureversus time; activate the channels of the lighting elements to generatea composite light; activate a color match algorithm to automaticallycreate respective drive signals for the channels of lighting elementsbased at least in part on the time-color profile and the respectivesignals representative of the composite light received from the lightsensors; and automatically provide the respective drive signals to thechannels of lighting elements to automatically vary a brightness leveland color level of respective ones of the channels of lighting elementsto produce the composite light along at least a portion of a daylightlocus that corresponds to values specified by the time-color profile fora current time.
 14. The system of claim 13 wherein the controller isoperable further to: cause a presentation of a user interface to receivethe user-selected input that specifies the adjustment for the time-colorprofile.
 15. The system of claim 13 wherein the controller causes apresentation of a user interface that represents time on a first axis,available values for one or more of brightness and color temperature ona second axis that is orthogonal to the first axis, and a plot of thevalues for one or more of brightness and color temperature versus time.16. The system of claim 13 wherein the respective drive signals arebased at least in part on the user-selected input and automatically varythe brightness level and the color level for respective channels oflighting elements to produce the composite light along at least aportion of the daylight locus that corresponds to the user-selectedinput.
 17. The system of claim 16 wherein the user-selected inputindicates a current activity of the user, and the respective drivesignals automatically vary the brightness level and the color level forrespective channels of lighting elements to produce the composite lightalong at least a portion of the daylight locus that corresponds to thecurrent activity of the user.
 18. The system of claim 16 wherein theuser-selected input indicates a desired sunlight scenario, the desiredsunlight scenario which is one of cloudless, partially cloudy, overcast,foggy, rainy, and snowy, and the respective drive signals automaticallyvary the brightness level and the color level for respective channels oflighting elements to produce the composite light along at least aportion of the daylight locus that corresponds to the desired sunlightscenario.
 19. The system of claim 16 wherein the user-selected inputindicates a desired one of at least two different color-time profiles,each of the at least two different color-time profiles specify valuesfor one or more of brightness and color temperature versus time, and therespective drive signals automatically vary the brightness level and thecolor level for respective channels of lighting elements to produce thecomposite light along at least a portion of the daylight locus thatcorresponds to the values specified by the desired one of the at leasttwo different color-time profiles for a current time.
 20. The system ofclaim 16 wherein the user-selected input indicates a geographiclocation, and the respective drive signals automatically vary thebrightness level and the color level for respective channels of lightingelements to produce the composite light along at least a portion of thedaylight locus that corresponds to lighting conditions that exist at thegeographic location.
 21. The system of claim 13 wherein the plurality oflighting element channels comprise a plurality of arrays combined on acommon digital bus, each of the plurality of arrays comprising at leastthree of the plurality of lighting element channels and at least two ofthe light sensors grouped within a common spatial region, the controllerwhich provides via the common digital bus respective drive signals tothe at least three channels of lighting elements of each of theplurality of arrays based at least in part on the respective signalsrepresentative of the composite light detected by the light sensors ofsuch array to form a plurality of closed feedback loops.
 22. The systemof claim 13 wherein the channels of lighting elements are selectivelyoperable to generate broad spectrum white light.
 23. The system of claim13 wherein the channels of lighting elements are selectively operable togenerate broad spectrum white light of color temperatures between at orgreater than 3000K and at or less than 5000K.
 24. The system of claim 23wherein the controller controls a total flux of blue light from arelative level of 1% to 100% of a maximum blue light flux within thebroad spectrum white light produced by the lighting elements.